Small computer assisted analysis of camera renograms Page: 2 of 13
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background is limited, with the camera face being small in comparison with
the area of the two kidneys and their outflow system. In the past, blood
background subtraction was usually done using a system of three probes; one
over the left subclavicular region (blood background) and one over each
kidney, in conjunction with an analog or digital computer The left sub-
clavicular region has been "validated" as a choice for the background area
by its close similarity with that actually found over a nephrectomy site
(1, 3, 4, 5).
The present system has the following additional advantages: visualiza-
tion of anatomical variations, precise patient positioning for the small
camera face, and the derivation of a numerical estimate of "true" individual
When renography is being repeatedly performed on the same patient,
important but small changes in renal function may be easier to detect after
blood background subtraction; for instance in the evaluation of function of
a newly transplanted kidney.
A scintillation camera with a computer has been used to determine the
ratio of blood background over each of the two kidneys to a non-renal region.
The patient is given 1.0 mCi 99mTc-labeled human serum albumin prior to the
renogram (Fig. 1). Generally, a scintiphoto of 50,000 counts is acquired.
Using the computer, regions are designated ("flagged") and the counts in
each region totalized. Thus the ratio of background region counts to the
right kidney nrd the nearly always different ratio of background region to
the left kidney can be obtained. During the analysis of the renogram, an
activity-time curve is generated for each of the three regions. With the
background ratio the "background" component from each of the kidneys can be
calculated. Possible choices for background areas are as follows:
1. An area including the upper aorta
2. An area including part of the spleen
3. As a "halo" about each kidney
4. Below the kidney, but lateral to the aorta and ureters.
At present we are not sure which area best represents the renal back-
SMALL COMPUTER ASSISTED ANALYSIS OF RENOGRAMS (SCAAR)
From the many methods of renal function analysis which have been
published, the method used and improved over the last 10 years by Britton
and Brown (1) was chosen for adaptation to a small computer. In particular,
it is hoped that the blood background subtraction and separation of uptake
and removal components of the renogram could add new information in a continu-
ing study by Atkins et al (7) on 99mTc DTPA and a comparison study of
renograms using 99mCc-DTPA and 1311-Hippuran. SCAAR was written for the
ND-812 Central Processor of a Med II System* which had been interfaced to an
Anger Camera. From the 16K memory (12 bit word length) over 8K are used for
image storage (two 64 x 64 frames). A large portion of the remaining 8K is
devoted to a conversational language interpreter. The remainder of the memory
is available for user-written programs which are stored on the disc ("text
buffers"). SCAAR uses two text buffers. The second text buffer is called by
the program and overlays the first text buffer.
The curves are generated from the total counts in designated
"flagged" areas (right kidney, left kidney and background) in the serial
scintiphotos stored on the disc. After injection of 99mTc-DTPA or 131[1-
iippuran, the scintiphotos are acquired every 15 seconds for a total period
*Nuclear Data Corp., Chicago
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Esser, P.D.; Bradley-Moore, P.R.; Atkins, H.L.; Robertson, J.S. & Ansari, A.N. Small computer assisted analysis of camera renograms, article, January 1, 1972; Upton, New York. (https://digital.library.unt.edu/ark:/67531/metadc1027737/m1/2/: accessed March 19, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.